To purify useful sugar components containing xylose from sulfuric acid hydrolysates, precipitation and processes of ion exchanges have been most frequently used. Among them, the ion-exchange method has been frequently used commercially, because it has low equipment costs and has been conventionally used. However, a large amount of wastewater containing a high concentration of salts is generated during regeneration of ion exchange resin, thus increasing wastewater treatment costs. For this reason, alternative technology capable of reducing the chemical substances usage and the amount of wastewater is required.
Recently, new separation technology such as electrodialysis has been reported as a desalting method of molasses and fermentation broth to use resources effectively. Korean Patent Laid-Open Publication No. 2008-0074687 discloses a method of producing xylose from tropical fruit biomass via hydrolysis, neutralization, precipitation, filtration, electrodialysis and ion-exchange steps. The bottleneck of electrodialysis process is that the ion-exchange membrane is easily contaminated by organic compounds. It is well known that this contamination reduces the efficiency of the device and shortens the life cycle of the membrane.
In order to solve this problem, pretreatment with a water softener or an anion exchange resin was attempted (Japanese Patent Laid-Open Publication No. Sho 54-67093). However, there is a limit to industrial application of this method because it has a problem that the costs rise up as several pretreatment steps and sub-materials are needed. Korean Patent Laid-Open Publication No. 2001-0107331 about a method of recovering lactic acid by an electrodialysis discloses a process of recycling ammonium sulfate and advantages such as efficiency and environmental advantages. However, electrodialysis still has a problems associated with the cost of membranes, the contamination of membranes and the stability of long-term operation, when it is industrially applied.